Photo: flickr/State Farm

Last year was a very bad year for wildfire damage across the U.S., and it’s only going to get worse. One way to counteract this increasing danger is to build smarter. A new study shows just how bad the problem has gotten, and suggests building smarter means being more intentional about where we build.

While many factors play into the increasing destruction, including drought and heat driven by climate change, rampant homebuilding in the so-called “wildland-urban interface,” or WUI, over the last few decades has really driven up the risks and the costs of fires, according to the study.

Published in the Proceedings of the National Academy of Sciences, it found that homebuilding in areas that were once sparsely settled grew rapidly over the two decades from 1990 to 2010, creating a collective area bigger than Washington state that’s now at risk of wildfire damage. In fact, even though the WUI represents less than one tenth of the land area of the contingous United States, 43 percent of all new homes built over the two decade study period were built there.

The proportion of new WUI area from 1990 to 2010 due to housing growth alone was greater than 80% in all but four northeastern states.
Illustration: Radeloff et al./SILVIS Lab/University of Wisconsin-Madison

This is problematic for two main reasons, according to the study. First, more fires can accidentally be started by people. Second, once a fire gets going at the WUI it’s harder to fight because of the human and property risk. Letting a fire just burn out is no longer an option when valuable property stands in its way.

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More than 10 million acres of the country were burned during the 2017 wildfire season with a cost of $2 billion, making it the most costly season ever according to the study. In California alone, five of the state’s worst wildfires on record took place last year.

With help from the U.S. Department of Agriculture and the U.S. Geological Survey, the authors were able to juxtapose information from the USGS’ National Land Cover Database on modified Census data. With this overlay, they determined that 9.5 percent, or 190 million acres, of the continental United States fell into the WUI in 2010, and that the number of houses within the WUI increased from 31 million to more than 43 million between 1990 and 2010.

Only the District of Columbia had negative absolute growth in the WUI (homes, people, and area) between 1990 and 2010.
Graphic: Radeloff et al./SILVIS Lab/University of Wisconsin-Madison

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Volker Radeloff, a professor of forest and wildlife ecology at UW-Madison and lead author on the study, told Earther that the WUI is a very attractive place to live.

“Many folks like to be close to nature,” he said. “The WUI is often also the place where it cheaper to own a house. So making cities both attractive and affordable is one important way to limit WUI development.”

Radeloff said that state and federal agencies can help support communities to come up with better land use plans that don’t exacerbate the WUI problem. Moving into a new suburban or exurban community may seem ideal for the privacy, affordability, and beauty it offers—but this type of development also can also up the wildfire risk. As metropolitan areas sprawl out more and more, it’s important to consider this impact when determining where to live.

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For communities that are already in the WUI, there’s an urgent need to become “fire-adapted,” according to the USDA. This includes “reducing wildland vegetation in and around high-risk areas, removing flammable vegetation directly around homes, and reducing the flammability of homes.”

The study is also the first to establish that 97 percent of the growth in the WUI over recent decades was attributable to homebuilding, while only 3 percent was due to vegetation regrowth into previously developed or agricultural areas.

Radeloff said that there was a lot of new WUI created east of the Mississippi, and even though the likelihood of fires is lower there than throughout the West, destructive wildfires do occur. In the West, there are far more public lands that are off-limits to development, and rough terrain along with arid climates also inhibit growth west of the Mississippi.

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Radeloff also warned that as the climate changes, the likelihood for wildfires will continue to go up.

“How much is hard to predict, but the current pattern of more fires and more houses in the path of those fires, is a dangerous combination,” he said.